Since we are using a force-wave simulation, the state variable
(delay element output) is in units of physical force (newtons).
Specifically,
. (The physical force is, of
course, 0, while its traveling-wave components are not 0 unless the
mass is at rest.) Using the fundamental relations relating traveling
force and velocity waves

where here, it is easy to convert the state variable to
other physical units, as we now demonstrate.

The velocity of the mass, for example, is given by

Thus, the state variable can be scaled by to ``read out''
the mass velocity.